The present invention relates to a method for controlling a laundry dryer with a variable drum rotation speed and a variable fan rotation speed. Further, the present invention relates to a corresponding laundry dryer.
The drum rotation speed in a laundry dryer is often constant during the drying cycle. Sometimes a variation of the drum rotation speed is used to optimize the drying performance. The drum rotation speed may be changed on the basis of many different situations. For example, a program for laundry made of wool requires a drum rotation speed higher than the usual drum rotation speed. In the wool cycle the higher drum rotation speed allows to stack the laundry around the wall of the laundry drum, so that damages to the laundry are avoided. Also in the case of laundry made of synthetic materials the drum rotation speed may be different. Further, during a specific drying cycle the drum rotation speed may change, for example due to inversions or to drum movement required to un-tangle possible knots in the laundry.
Any change to the drum rotation speed may have a not negligible impact into the overall machine performances. The drying cycle is usually negatively affected when the laundry drum is not rotating at a standard speed for which the drying performances are maximized. However, as mentioned a above, variations of the drum speed from the standard speed are possible to meet different laundry drying requirements
In particular, the variation of the drum rotation speed in a laundry dryer with a heat pump system disturbs the overall performances of the laundry dryer.